Using Video Baluns HELP

[robertjsmyth 0]

Hi, I have tried to use video Baluns on a Cat5 Cable which is no more than 150m long, however the picture doesnt come through at the other side, a distorted muffled collapsed picture shows but thats all. Technicaly the RJ45s are terminated correctly and have been tested using a Cat5 tester (this only confirms correct wiring and polarity but not quality of the cable) Can anyone help in any way????? The Cat5 cable doesnt go through ANY routers, it does however terminate at either end on Krone Blocks where I have Cat5 connected on to terminate at the rj45 connectors. the main trunk line connecting the krone blocks is a 30 pair line which includes telephone lines and 1 ethernet connection.

 

I tried an equalizing D.A. and this didnt change anything.

 

I have a small 8" Monitor/Television which I have tried on the receiving side and...... YAHOO! blush ........it works perfectly. Change it to an ordinary TV/Monitor (still using the baseband composite videe and NOTHING! (a collapsed picture appears on some of the ordinary tv/monitors) confused confused confused

 

So I suspect that it may well be something to do with one of the following:

 

1. My 8" Monitor may well be electrically isolated? (its powered off the mains by a regulated 12v supply)In which case a video isolation transformer might work??????

 

2. Ordinary Monitors are terminating the video signal far too much?

 

Any suggestions would be GREATLY appreciated!

P.S. I have ordered Ground Loop Isolators in the hope that they may sort it out but wont have them for a few day.

Any help in the meantime would be greatly appreciated

Thanks,

R

[robertjsmyth 0]

Using a standard multimeter the Earth Potential difference is 2.5 volts AC and .5 volts DC.

 

I tried isolating the balanced portion of the ground signal (connection between the baluns)(indeed even the unbal portion) to no avail.(i did'nt realistically think this would work but worth a try.)

[robertjsmyth 0]

Problem Solved!

 

I connected Two Ground Loop isolators bought from foresight-cctv.com in to the line (One at the TX side and one at the RX side) It actually only required one at the RX side to fix the problem but for electrical safety I put one at each end.

 

Thanks for your assistance in this!

[rory 0]

Glad you got it soughted out, guess everyone else was busy

I just got back myself so just had the chance to check it out ...

 

good luck, and dont be a stranger.

 

Rory

[normicgander 0]

What kind of video UTP baluns did you use? When you insert the baluns on end end the twisted pair circuit "floats" and the tx and rx ends are ground isolated from eachother. It sounded like a reverse polairty issue. Did the original baluns bench test test ok?

[robertjsmyth 0]

Hi,

I will check the make of the original baluns. the new video isolators come from forsight-cctv.com. On a bench test the original baluns worked fine. i actually thought it might have been a polarity reversal, it had all the hallmarks of a polarity reversal but alas no!

 

feel free to ask me more, id be delighted to tell u anything you want to know,

 

Thanks, Robert

[Soundy 1]

From your description, it sounds like you simply had the polarity switched on one balun. Most baluns, passive models at least, require you use the same polarity at both ends - the MUXLAB ones I use, for example, are marked TIP and RING on the terminals: the TIP on one must be connected to the TIP on the other, and RING to RING, or you get a scrambled picture.

[robertjsmyth 0]

These particular baluns terminate on rj45 sockets for direct connection to a cat5 cable. I originally tested these using an electronic cat5 tester that I have. This tester confirms the correct polarity of each connection ie. pin1 correctly connected to pin1 at each end. The only other possibility is that the baluns are internally incorrectly wired (which I doubt) but I will check asap!